A method for suppressing the generation of transient phenomena, which impacts electric power systems and electric power equipment, by controlling the opening or closing timing of a circuit breaker for power, has been proposed (e.g. see Non-patent Document 1).
A specific invention to implement this method for suppressing the generation of transient phenomena, which has already been proposed, is a switching controlgear of circuit breaker which switches circuit breaker contacts at a timing between a current zero point and a peak value of the interrupting current when the current is interrupted, and controls the closing timing of the circuit breaker contacts according to the type of load when the circuit breaker contacts is closed (e.g. see Patent Document 1).
Another invention which has already been proposed focuses on the fact that a high frequency reignition surge is not generated at a current phase 0° point of the final break point of the circuit breaker when a shunt reactor connected to a bus line is parallel-off controlled in order to compensate for a charge current or adjust voltage of the electric power system, a single phase voltage is input to a circuit breaker opening control device using an voltage transformer, then each current phase is calculated by the circuit breaker opening control device based on the phase of the single phase voltage, and an opening instruction is output to the circuit breaker so that each phase current which flows through the shunt reactor can be interrupted at zero point (e.g. see Patent Document 2).
Both switching controlgear of circuit breakers according to Patent Documents 1 and 2 have a function to delay the output timing of an opening command signal or a closing command signal to the circuit breaker, so as to cause the circuit breaker to open or to close at a predetermined phase when the opening command signal or closing command signal is detected. Such a switching control for a circuit breaker is called “synchronous opening control” or “synchronous closing control”.    Patent Document 1: Japanese Patent Application Laid-Open No. H03-156820    Patent Document 2: Japanese Patent Application Laid-Open No. H06-20564    Non-patent Document 1: “Controlled switching of HVAC circuit breakers: Guide for application lines, reactors, capacitors, transformers. SC13”, ELECTRA No. 183, p. 43, (1999)
All the above-mentioned switching controlgear of circuit breakers detect a zero cross point of power system voltage or main circuit current after an opening command signal or closing command signal is input to the switching controlgear, and control the output delay timing of the opening command signal or closing command signal to the circuit breaker based on this zero cross point.
A timing chart of a conventional synchronous opening control, shown in Non-patent Document 1, will be described with reference to FIG. 12. In FIG. 12, tseparate indicates an opening timing of the circuit breaker contacts, that is, a desired opening phase of main circuit current which opens the circuit breaker contacts.
Ttarget is an opening timing of tseparate converted into time, using the zero cross point (timing at current phase)0° of a main circuit current waveform as a reference. In an actual circuit breaker, an arc time Tarcing, when an arc current flows, exists, so interruption completes electrically when Tarcing time elapsed from the timing of tseparate, which is the current zero point.
For both control devices of Patent Documents 1 and 2 as well, the synchronous opening delay time Tdelay is calculated so that the circuit breaker contacts open at the timing of tseparate, when the time of the total of synchronous opening delay time Tdelay and opening operation time Toperating elapses, using the zero cross point of the main circuit current waveform as a reference, just like the timing chart shown in FIG. 12.
In a case of a conventional switching controlgear, if the opening command signal is input to the control device at a timing of tcommand in FIG. 12, [the switching controlgear] must wait until the next zero cross point of the main circuit current waveform is detected. In FIG. 12, this wait time is indicated by a zero cross point wait time TW. After a further wait for the synchronous opening delay time Tdelay from the detected next zero cross point, the control device outputs the opening command signal to the circuit breaker at a timing of tcontrol.
In other words, the total wait time to be generated from the input of the opening command signal to the control device to the output of the opening command signal to the circuit breaker is “Ttotal=TW+Tdelay”. This length of the total wait time Ttotal depends on the input timing of the opening command signal and the target opening phase, and could reach 2 cycles at most. Also depending on the operation performance of the control device, N cycles (N=1, 2, . . . ) of wait time may be additionally generated.
The synchronous closing control is also represented by a similar timing chart, where a similar total wait time is generated. In the case of the synchronous closing control, however, control is normally performed using the zero cross point of the power system voltage as a reference, and control is also performed considering the pre-arc time of the circuit breaker.
In this way, in the case of the conventional switching controlgear of circuit breaker, a maximum of 2 cycles of idle time is generated to perform synchronous opening control or synchronous closing control. Also depending on the computing performance of the switching controlgear, N cycles (N=1, 2, . . . ) of additional idle time is generated.